are the largest subgroup of crustaceans, and include most of the animals that non-experts recognise as crustaceans, including crabs, lobsters, shrimps, mantis shrimps and krill
. They also include the huge group of amphipods
, and the only substantial group of land-based crustaceans, the isopods (woodlice
or sowbugs and related species).
The classification of crustaceans is currently being debated, and the Malacostraca are regarded by some authors as a class and by others as a subclass.
Their characteristics include:
- Five pairs of walking legs
- The first pair of legs are often modified to form pincers
- Cephalothorax covered by a carapace
- Abdomen behind, often used for swimming
- Appendages near the mouth; these are called maxillipeds
- Two-chambered stomach
- Centralised nervous system